1. Field of the Invention:
The present invention relates to a feed unit apparatus made up of a ball screw mechanism integrally combined with a linear guide apparatus.
2. Description of the Prior Art:
A prior art feed unit apparatus in which a ball screw mechanism and a linear guide mechanism are combined with each other is disclosed, for example, in Japanese Utility Model Laid-Open Publication No. 61-61362. In this apparatus, the feed unit apparatus comprises a feed screw shaft (ball screw shaft) having a spiral groove in an outer surface, a linear guide rail (guide rail) disposed in parallel with the feed screw shaft, and a nut block including a linear guide means movably fitted into the linear guide rail in an axial direction and a nut section threaded around the feed screw shaft so that the linear guide means and the nut section are integrally formed with each other. A rotational movement of the nut block with respect to the feed screw shaft is prevented by the linear guide means.
However, in such a prior art feed unit apparatus, the linear guide rail has a recessed groove extending axially and opening upwardly, and the nut block is guided to move rectilinearly through rolling members within the recessed groove in accordance with rotation of the feed screw shaft disposed in the recessed groove. As a result, since the dust sealing against the feed screw shaft within the recessed groove and the rolling members for linear guiding is not sufficient, then the feed unit apparatus is used in a welding robot or the like, sputters produced during welding, dust, or the like are apt to enter the feed screw shaft and the rolling members for the linear guiding. Accordingly, problems are involved in that a malfunction is apt to be caused and, when the feed unit apparatus is used in a clean room, lubricating oil is scattered in the room contaminating the environment.